Lubricator valves are valves used downhole to allow long assemblies to be put together in the well above the closed lubricator valve with well pressure further below the closed lubricator valve. These valves are frequently used in tandem with sub-surface safety valves to have redundancy of closures against well pressures below. Valves are also used downhole for other isolation purposes.
Lubricator assemblies are used at the surface of a well and comprise a compartment above the wellhead through which a bottom hole assembly is put together with the bottom valve closing off well pressure. These surface lubricators have limited lengths determined by the scale of the available rig equipment. Downhole lubricators simply get around length limitations of surface lubricators by using a lubricator valve downhole to allow as much as thousands of feet of length in the wellbore to assemble a bottom hole assembly.
In the past ball valves have been used as lubricator valves. They generally featured a pair of control lines to opposed sides of a piston whose movement back and forth registered with a ball to rotate it 90 between an open and a closed position. Collets could be used to hold the ball in both positions and would release in response to control pressure in one of the control lines. An example of such a design can be seen in U.S. Pat. Nos. 4,368,871; 4,197,879 and 4,130,166. In these patents, the ball turns on its own axis on trunnions. Other designs translate the ball while rotating it 90 degrees between and open and a closed position. One example of this is the 15K Enhanced Landing String Assembly offered by the Expro Group that includes such a lubricator valve. Other designs combine rotation and translation of the ball with a separate locking sleeve that is hydraulically driven to lock the ball turning and shifting sleeve in a ball closed position as shown in U.S. Pat. No. 4,522,370. Some valves are of a tubing retrievable style such as Halliburton's PES® LV4 Lubricator Valve. Lock open sleeves that go through a ball have been proposed in U.S. Pat. No. 4,449,587. Other designs, such as U.S. Pat. No. 6,109,352 used in subsea trees have a rack and pinion drive for a ball and use a remotely operated vehicle (ROV) to power the valve between open and closed positions claiming that either end positioned is a locked position but going on to state that the same ROV simply reverses direction and the valve can reverse direction.
What is lacking and addressed by the present invention is a more elegant solution to a downhole ball type lubricator valve. One of the features is the ability to translate the ball for the purpose of locking open a ball that normally rotates between open and closed on its own axis. Another feature is a method of manufacturing parts that must be longitudinally split so that they retain the original bore dimension despite the wall removal occasioned by longitudinally splitting the part. Yet another feature is the ability to assemble components to a given overall dimension so as to accurately set preload on biased seats that engage the ball.
In one embodiment, the annular piston that actuates the valve is replaced with at least one rod piston and the space made available with this change allows the addition of a seal to prevent leakage under high differential pressure conditions from the uphole to the downhole direction.
These and other features of the present invention will be more readily apparent to those skilled in the art from a review of the preferred embodiment and associated drawings that are described below while recognizing that the full scope of the invention is determined by the claims.